Multiprotocol Label Switching (MPLS) has become the preeminent technology for the public Internet and for private internets by improving the performance of network layering and providing greater flexibility in the delivery of routing services. Learn how the speed of MPLS is proving to be the most effective way to direct internet traffic.

This chapter is from the book

This chapter is from the book

Introduction

This chapter explains why label switching networks and Multiprotocol Label
Switching (MPLS) have become key players in the emerging multiservice public
Internet and private internets. It explains the problems associated with
conventional IP routing procedures and introduces the concepts of the
alternative: label switching. The chapter also introduces the idea of quality of
service (QOS) and explains its importance, as well as the importance of label
switching to QOS. The chapter concludes with an example of a label switching and
QOS network operation at a label switching router (LSR).

What is Label Switching?

The basic concept of label switching is simple. To show why, let's
assume a user's traffic (say, an email message) is relayed from the
user's computer to the recipient's computer. In traditional internets
(those that do not use label switching), the method to relay this email is
similar to postal mail: a destination address is examined by the relaying entity
(for our work, a router; for the postal service, a mail handler). This address
determines how the router or mail handler forwards the data packet or the mail
envelope to the final recipient.

Label switching is different. Instead of a destination address being used to
make the routing decision, a number (a label) is associated with the packet. In
the postal service analogy, a label value is placed on the envelope and is
thereafter used in place of the postal address to route the mail to the
recipient. In computer networks, a label is placed in a packet header and is
used in place of an address (an IP address, usually), and the label is used to
direct the traffic to its destination.